This invention relates to apparatus and methods for determining physiological or metabolic status of an organism by measuring and comparing effects of applied metabolic stresses. More specifically, this invention includes an apparatus and a method for monitoring the adaptive control of oxygen consumption to measured changes in stress. Data presented in this invention indicate that monitoring this adaptive process is an efficient means of delimiting the metabolic capacity of the organism.
It has long been thought desirable to obtain a general measure of physical health by assessing the overall metabolic capability of an organism. Metabolic tests, for example, have been a part of standard physical examinations for presumably healthy individuals for years. In contrast to attempts to diagnose specific illnesses or dysfunctions, these measurements attempt to assess the efficiency and general integrity of the physiological systems of the organism as a whole. For example, in mammalian systems, the relationship of the respiratory, cardiopulmonary, and even endocrine systems, as well as their individual capacities and status, impacts on the overall well-being of the mammal. All organisms can be assumed to be in better or poorer health depending on the individual status and integration of a number of metabolic systems.
It is, of course, desirable to have available a method for quantification of what might loosely be called good or poor health or efficiency level for the organism. There is a particular interest in assessing the effects of externally imposed environmental factors on the organism and evaluating the effects of potentially toxic substances. It is now generally thought that certain environmental factors, such as, for example, poor air quality, certain chemicals, which are found as contaminants in food, water or air, and general dietary factors, which may produce effects which are not sufficiently acute to result in measurable specific symptoms except in isolated individuals, may, in fact, cause a general diminution of well being in the population as a whole. Also, it is clear that there are potential toxic effects of medications which are associated with only vague symptoms, such as moderate discomfort or nausea, which do not uniformly impact all members of the subject population. These seem not at present to be amenable to effective pretesting, because of a lack of a quantitative system of measuring impact on the overall organism. In addition, it would be desirable to test the direct effects of drugs at as low a dosage level as is possible, and to determine the physical condition of healthy animals and human beings.
The present invention provides for quantitative assessment of these factors by using adaptive respiratory capacity as a measure of overall metabolic status. The adaptive respiratory capacity of an organism is measured by ascertaining the rate of consumption of oxygen as a function of stress in various forms.
This method employs a respirometer of a design which, itself, represents an improvement over the presently available means for assessing oxygen uptake in subject organisms, and which has also a means for applying and varying stress to the subject organism. Many devices have been designed to monitor the respiratory rate of a subject while under situations of controlled environmental situations. However, devices which measure metabolic capacity by measuring the adaptive respiratory responses of organisms to sequentially applied quantitatively measured stresses do not exist. Since most respiratory monitoring devices communicate with ambient air, they do not readily facilitate reduced oxygen pressure as one possible form of environmental stress. For example, U.S. Pat. No. 3,401,683 to Webb discloses an apparatus wherein the subject wears a helmet which causes exhaled gases to be drawn into the monitoring device. Thus, if testing at reduced pO.sub.2 is desired, the entire monitoring device must be enclosed in the test chamber. In U.S. Pat. No. 3,523,529 and U.S. Pat. No. 3,507,146, devices are disclosed which are worn by the subject and measure oxygen uptake through a breathing mask or similar apparatus attached to the nose and mouth in order to isolate the exhaled air. Resulting metabolic rate calculations must take into account effects of such cumbersome monitoring devices. Because of the above considerations, present systems severely limit the variety of organisms which may be subjected to metabolic analysis by respiratory techniques, do not measure the organisms adaptive respiratory response to stress and do not use the adaptive responses as a means for measuring metabolic disfunction. The present invention offers the capacity to measure not simply the oxygen consumption of any organism which is capable of respiration, but also provides a means to control stress levels by adjusting the oxygen concentration, increasing temperature, exercise intensity, or other physical parameters and in these fashions measure the adaptive respiratory response of the organism to these stress and use these responses to detect changes in metabolic function.